1. Field of the Invention
The present invention relates to a tire tube and an apparatus for manufacturing the tire tube, and particularly to a tire tube including an air chamber filled with air and a sealant chamber filled with a sealant and an apparatus for manufacturing the tire tube.
2. Description of Related Art
FIG. 1 is a transverse sectional view of a wheel mounted with a tube containing tire including a sealant chamber; FIG. 5 is a flow chart showing steps of manufacturing a tube; and FIG. 6 is a partial perspective view of an extrusion-molding machine for extrusion-molding a tube material.
As shown in FIG. 1, a rim R of a motorcycle wheel is connected to a hub (not shown) via wire spokes (not shown). A tube containing tire T including a tire 1 and a tube 2 contained in the tire 1 is mounted on the rim R. The tube 2 includes a peripheral wall 4 and a partition wall 5 for partitioning the inside surrounded by the peripheral wall 4 into two parts. The peripheral wall 4 is composed of an air chamber peripheral wall 41 positioned radially inward of the tube 2, and a sealant chamber peripheral wall 40 positioned radially outward of the tube 2. The partition wall 5 is molded integrally with the peripheral wall 4.
An air chamber 3, which is surrounded by the air chamber peripheral wall 41 and the partition wall 5 in an approximately circular shape in cross-section, is filled with air. A sealant chamber 7, which is surrounded by the sealant chamber peripheral wall 40 and the partition wall 5 in an approximately arcuate shape, is filled with a known liquid sealant 8. The air chamber peripheral wall 41 has an air valve 6 for filling the air chamber 3 with air.
As shown in FIG. 5, a process of manufacturing the tube 2 includes a material kneading step, a tube material extrusion-molding step, a cutting step, an air valve mounting step, a joining step, and the like.
A material composed of a crude rubber kneaded during the material kneading step is extrusion-molded into a tube material 2′ by an extrusion-molding machine during the tube material extrusion-molding step. The tube material 2′ is cut into a specific length during the cutting step; an air valve 6 is mounted at a suitable position on the air chamber peripheral wall 41 during the air valve mounting step; and both ends of the tube material 2′ are joined to each other during the joining step. After that, the material 2′ is subjected to a vulcanizing step and a sealant filling step to obtain a finished tire tube.
As shown in FIG. 6, a nozzle 12 of an extrusion-molding machine 11 has surface lubricant delivery ports 14a and 14b and surface lubricant suction ports 13a and 13b for supplying and discharging a surface lubricant such as talc into the air chamber 3 and the sealant chamber 7, respectively.
The general sealing performance of a tire is improved by increasing the charged amount of a sealant 8 into the sealant chamber 7, thereby increasing the thickness “t” of the sealant 8; however, when the charged amount of the sealant 8 is increased, the weight of the tire tube 2 is increased to thereby degrade the durability of the tire tube 2 at the contact surface with a tire 1.
In this way, since the durability of the tire tube 2 is incompatible with the sealing performance of the tire tube 2, the thickness “t” in the diameter direction of the sealant 8 in the sealant chamber 7 is required to be specified when considering the sealing performance and durability. According to the related art; however, the relationship between the thickness “t” of the sealant 8 in the sealant chamber 7 and the sealing performance/durability has failed to be examined. Therefore, in the tires of the related art, the thickness of the sealant 8 has not been suitably determined. Therefore, it is difficult to make the sealing performance compatible with the durability of the tire.
In the above described related art extrusion-molding machine 11, while talc is delivered in regions forming the air chamber 3 and the sealant chamber 7 from the different surface lubricant delivery ports 14a and 14b respectively, delivery means such as a pump for imparting a delivery pressure is common to the surface lubricant delivery ports 14a and 14b. Accordingly, if a delivery load at one of the surface lubricant delivery ports becomes larger than that at the other surface lubricant delivery port due to some external cause, the delivery force applied by the pump is concentrated on the other surface lubricant delivery port side. As a result, while the surface lubricant in an excessively larger amount is delivered from the latter surface lubricant delivery port with the small delivery load, the amount of the surface lubricant delivered from the former surface lubricant delivery port with the large delivery load becomes insufficient because a specific deliver pressure is not applied to the delivery port.
As shown in FIG. 6, for example, when extrusion-molding is performed when the delivery port 14a is located on the upper side and the delivery port 14b is located on the lower side, a delivery load at the upper delivery port 14a is larger than that at the lower delivery port 14b due to gravity applied to the tube. As a result, while the surface lubricant is delivered in a large amount from the lower delivery port 14b, the surface lubricant is not delivered in a sufficient amount from the upper delivery port 14a. 